The fourth edition of the TNM Classification was published in 1987,1 and a revision in 1992.2 It was the result of efforts by all national TNM Committees towards a worldwide uniform classification. The classifica tion criteria are identical with the fourth edition of the Manual for 3 Staging of Cancer of the American Joint Committee on Cancer (AJCC). Although the classification has found wide acceptance, some workers have pointed out that individual definitions and rules for staging are not sufficiently detailed. This can lead to inconsistent application of the clas sification. the antithesis of standardization. This source of differences in interpretation applies not only to the classification of individual organs but also to the general rules of the system, especially to the definitions of the requirements for the pathological classification (pT, pN). These are specified only for carcinoma of the breast; for other sites, reference must be made back to the general rules. which can lead to variable interpreta tions. The TNM Project Committee of the UICC has addressed this prob lem and collected and considered the criticisms and suggestions from the national TNM Committees as well as from cancer registries, oncolo gical associations and individual users. The result was the decision to complement the 4th edition of the TN M Classification 1.2. 3 with the publi cation of a TNM Supplement containing recommendations for the uni form use of TNM."

This is a classification of tumours and tumour-like lesions of the gall- bladder and extrahepatic bile ducts, including the ampulla of Vater. Although most of the lesions are found in all three sites, variations in frequency of the histological types occur and will be noted. The incidence of carcinoma of the gallbladder varies in different parts of the world. Variation is also found in different ethnic groups within the same country. In the United States, for example, carcino- ma of the gallbladder is more common in American Indians than in Caucasians or in Blacks; the rate among female American Indians is 21 per 100000 compared with 1.4 per 100000 among Caucasian fe- males. In Latin American countries, the highest rates are found in Chile, Mexico and Bolivia. In other countries, such as Japan, the inci- dence rates are intermediate between those of American Indians and those of Caucasians. Despite certain features in common, carcinomas of the gallblad- der and carcinomas of the extrahepatic bile ducts show a number of differences. Gallbladder carcinomas are usually associated with cholelithiasis and have a strong female predominance. In contrast, extrahepatic bile duct carcinomas are seen less often, occur in both sexes with equal frequency, are usually not associated with choledo- cholithiasis, produce early biliary obstruction, and are better differen- tiated histologically as a group. Moreover, they are seen in patients with primary sclerosing cholangitis and ulcerative colitis.